It has been demonstrated in the experimental uremic animal that chronic uremia results in abnormal bone collagen cross-link ratios and that 25OH cholacalciferol as well as diphosphonates reverse the lesion both biochemically and histologically. Short term (6 mo.) 25-hydroxycholecalcierol treatment of patients with advanced renal failure also resulted in similar changes. Additional accomplishments include documentations of vitamin D action on bone in the absene of parathyroid hormone and that diabetes mellitus leads to progressive loss of skeletal mass in children and adults. BIBLIOGRAPHIC REFERENCES: Teitelbaum, S.L., Rosenberg,E.M. Bates, M. and Avioli, L.V.: The Effects of Phosphate and Vitamin D Therapy on Osteopenic, Hypophosphatemic Osteomalacia of Childhood: A Morphometric Study. Clin. Orthop. and Rel Res. (to be published May, 1976). Hahn, T.J., Scharp, C.R., Halstead, L.R., Haddad, J.G., Karl, D.M. and Avioli, L.V.: Parathyroid Hormone Status and Renal Responsiveness in Familial Hypophosphatemic Rickets. J. Clin. Endocr. and Metab. (Nov., 1975).